1. LIGO Charging Workgroup Telcon 12/12/2006 1 GRS LSC_Charging_061210.ppt K. Sun UV LED Charge Management Progress Report LIGO Charging Workgroup Telcon 9:00 am December 11, 2006 Ke-Xun Sun

2. LIGO Charging Workgroup Telcon 12/12/2006 2 GRS LSC_Charging_061210.ppt K. Sun UV LED Lifetime Beats Mercury Lamp UV LED Emission Lifetime > 5,077 Hours –As of Dec. 1, 2006 (5 PM) –Power stability within measurement error (~5 %) –Fast modulation with 10% duty cycle –Compared with mercury lamp lifetime of 5000 hrs UV LED Spectral Stability –Central wavelength ~256 nm –No spectral shift observed in all three measurements (start, 1000 hrs, and 3000 hrs)

3. LIGO Charging Workgroup Telcon 12/12/2006 3 GRS LSC_Charging_061210.ppt K. Sun UV LED Lifetime Experiment HP Signal Generator Nitrogen Chamber ILX laser Driver GPIB Computer Modulation GPIB Amp Scope or Digitizer UV LED UV detector

4. LIGO Charging Workgroup Telcon 12/12/2006 4 GRS LSC_Charging_061210.ppt K. Sun UV LED Operated for AC Charge Management UV LED Direct Readout Driving Signal Signal from UV Photodiode Signal to UV LED 1 msec

5. LIGO Charging Workgroup Telcon 12/12/2006 5 GRS LSC_Charging_061210.ppt K. Sun Relative Power Stability

6. LIGO Charging Workgroup Telcon 12/12/2006 6 GRS LSC_Charging_061210.ppt K. Sun Relative Spectral Stability

7. LIGO Charging Workgroup Telcon 12/12/2006 7 GRS LSC_Charging_061210.ppt K. Sun UV LED Charge Management Plan at Stanford UV LED system development –LISA /LIGO dual use –Must have flexible modulation capability –High power version for LIGO only –Supply the UV LED system to LIGO Labs Vacuum chamber commission and renovation –UV grade fused silica window –Gauges AC charge management system for LIGO proof mass charging/discharging Remote measurement of surface potential Substrate direct charge management Conductive coating charge management Modeling efforts will parallel

8. LIGO Charging Workgroup Telcon 12/12/2006 8 GRS LSC_Charging_061210.ppt K. Sun High Vacuum Chamber for LIGO UV Experiment Vertical vacuum jar good for suspension Ion Pump 10-7 to 10-9 torr

9. LIGO Charging Workgroup Telcon 12/12/2006 9 GRS LSC_Charging_061210.ppt K. Sun UV Grade Fused Silica Transmission Good for LIGO Chamber Window

10. LIGO Charging Workgroup Telcon 12/12/2006 10 GRS LSC_Charging_061210.ppt K. Sun BK7 Glass Transmission Curve Cutoff at ~330 nm

11. LIGO Charging Workgroup Telcon 12/12/2006 11 GRS LSC_Charging_061210.ppt K. Sun Conductive Coating Patterns UV transparent photoelectron dot (low work function material) UV transparent, weakly conductive coating LIGO test mass

12. LIGO Charging Workgroup Telcon 12/12/2006 12 GRS LSC_Charging_061210.ppt K. Sun UV Illumination Schemes for UV AC Charge Management Direct illumination –UV mercury lamp is routinely used for attachment removal –UV LED has sufficient power for cw or pulsed direct illumination –Need to make sure no solarization (tanning) effect Illumination on coatings –Thin Au coating on non- critical portions of test mass and suspension structure –Photoelectric effect on thin Au coating is common mechanism for photocathode –Higher throughput in charge control

13. LIGO Charging Workgroup Telcon 12/12/2006 13 GRS LSC_Charging_061210.ppt K. Sun Coordinating with LIGO Project Let us know what we can help –Gregg’s and Charging List’s emails very helpful –LIGO site configuration info –Items needed –Requirements –Schedule and test plan –Some LIGO funds?